Ultrafast laser inscribed Yb:KGd(WO_4)_2 and Yb:KY(WO_4)_2 channel waveguide lasers

Bain, F. M.; Lagatsky, A.A.; Thomson, Robert R.; Psaila, N. D.; Кулешов, Н. В.; Kar, A. K.; Sibbett, W.; Brown, C.T.A.

doi:10.1364/oe.17.022417

Cited by 80 publications

(48 citation statements)

References 23 publications

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“…Since the LYB:Eu is a potential laser crystal [10], these observations are of strong interest when considering possibilities to tune both structural and optical properties of this material by direct laser writing, especially for weaker crystal modifications related to waveguide writing for laser amplification applications [11][12][13][14][15]. Moreover, since such crystal is a low symmetry crystal, intensity thresholds for laser-induced modifications should significantly depend on the considered crystal orientation [16].…”

mentioning

confidence: 99%

Raman and fluorescence correlative microscopy in polarized light to probe local femtosecond laser-induced amorphization of the doped monoclinic crystal LYB:Eu

Marquestaut

Dussauze

Petit

et al. 2013

Chemical Physics Letters

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An endless increasing number of laser/material interaction studies above laser-induced modification thresholds have been carried out over the past decade, either for undesirable laser-induced damages, for example in high power laser systems in relation with material ageing and material optical quality, or for profitable laser-induced alteration from direct laser writing (DLW) techniques. DLW is at the root of many applications such as the fabrication of micro-capillaries for micro-fluidics issues, waveguide writing, optical memories, etc... New functionalities based on enhanced optical property modifications can further be developed by tailoring the material chemical composition with photosensitive agents, in order to improve its interaction with the writing laser [1]. Thus, for the laserinduced linear properties, DLW can lead to plasmonic enhancement from nanoparticles [2], fluorescence from metallic clusters [3] or oxidation degree modifications of rare earth ions [4]. For the nonlinear properties, second-harmonic generation (either from locally buried electric field [5] or from locally laser-induced micro-crystallization [6]) or third-harmonic generation [7] can be obtained.Most of the studies are related to isotropic material modifications (density change, oxidation degree changes, local crystallization, etc...) [1] while much less refer to laser-induced modifications inside crystals, being isotropic [8] or not [9]. Still, laser-induced modifications inside a crystal matrix are promising research topics for perennial optical devices and applications, thanks to the intrinsic stability of the crystalline matrix arrangement, but also for waveguide applications for efficient laser and Raman amplification as well as for frequency conversion. Generally, laser-induced modifications lead to local index change, local melt, local amorphization or even local recrystallization, giving rise to differential optical properties with respect to the non-irradiated bulk matrix.In this work, we have studied the local modification induced by a femtosecond (fs) near infrared NIR laser on a monoclinic crystal matrix LYB, highly doped with Eu 3+ rare earth ions. Thanks to point-bypoint optical mapping in both Raman and fluorescence micro-spectroscopy in polarized light, we report on the local changes corresponding to partial amorphization of the LYB:Eu crystal, resulting to significant reshaping of the spectral properties in polarized light. The optical specificities of lowsymmetry crystal optics were properly taken into account, to provide meaningful interpretation of the modified Raman and fluorescence spectra. Strong laser-induced amorphization of the crystal matrix have been evidenced. An accurate characterization of the spectral variations of spatial distribution have shown (i) an homogeneous degree of amorphization within a volume at least two times larger than the laser-structuring voxel, and (ii) a variation of density within the amorphous region.Such study shows that both Raman and fluorescence spectroscopies are relevant ...

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mentioning

confidence: 99%

Raman and fluorescence correlative microscopy in polarized light to probe local femtosecond laser-induced amorphization of the doped monoclinic crystal LYB:Eu

Marquestaut

Dussauze

Petit

et al. 2013

Chemical Physics Letters

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“…6. All structures consisted of two tracks inscribed next to each other at a separation of 20 m. Microspectroscopy mapping was performed on structures written at different pulse energies, which gave different guiding and lasing performance.…”

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confidence: 99%

Microspectroscopy of ultrafast laser inscribed channel waveguides in Yb:tungstate crystals

Bain

Silva

Lagatsky

et al. 2011

Applied Physics Letters

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We report microspectroscopy measurements of crystalline channel waveguides fabricated in Yb: KGd͑WO 4 ͒ 2 and Yb: KY͑WO 4 ͒ 2 using the ultrafast laser inscription technique. From these measurements we find that densification of the WO 2 W bridge in the double tungstate crystal lattice is responsible for the refractive index increase, which creates the waveguide confinement. We identified that shifts toward lower energies in the ϳ760 cm −1 Raman mode indicate regions, which guide light polarized along the crystallographic b axis, while higher energy shifts in the 682 and 898 cm −1 Raman lines correspond to guiding regions for light polarized along the crystallographic a axis. ͓Yb: KGd͑WO 4 ͒ 2 and Yb: KY͑WO 4 ͒ 2 ͔, and Li: NbO 3 ͑Li:NbO͒. 7 During ULI, ultrashort-pulse radiation is tightly focused inside a dielectric material, resulting in high electric field intensities, which induce nonlinear processes such as multiphoton absorption and avalanche ionization, and lead to high temperatures and pressures through an induced microplasma. The plasma recombines with the lattice through energy transfer and this induces a modification to the material structure. In crystalline materials, this modification often takes the form of a void structure due to expansion of the material in the focal volume. This expansion induces a strain field in the material surrounding the void, which in turn leads to a refractive index modification via the photoelastic effect. However, the physical changes to the crystalline media and the mechanisms responsible for the resulting stress are not well understood. Two nondestructive techniques, which can be used to investigate the induced microscale modifications in the crystalline material are confocal microluminescence ͑ -PL͒ and micro-Raman ͑ -Raman͒ measurements. 8,9 These techniques involve recording the localized luminescence and Raman spectra from small volumes ͑Ͻ1 m 3 ͒ in and around the waveguide structure. By the observation and interpretation of any changes to the output spectra, such as intensity, peak wavelength, and spectral width, information on localized lattice damage, stress, and disorder can be extracted.Here we report two-dimensional ͑2D͒ microspectroscopy mapping of waveguides fabricated in crystalline Yb 3+ : KGd͑WO 4 ͒ 2 ͑Yb:KGdW͒ and Yb 3+ :KY͑WO 4 ͒ 2 ͑Yb:KYW͒ using ULI. The structural changes to the lattice, which were responsible for the localized refractive index variation, have been identified.Details of the waveguide fabrication and their laser performance can be found in Ref. 6. All structures consisted of two tracks inscribed next to each other at a separation of 20 m. Microspectroscopy mapping was performed on structures written at different pulse energies, which gave different guiding and lasing performance. It was observed that in Yb:KGdW, guiding of light polarized along the crystallographic a axis occurred in regions above and below the central crack ͓Fig. 1͑a͔͒, which was formed during waveguide fabrication. Conversely, guiding of light polarized along the ...

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“…The method was introduced by Davis et al [101] and it had been applied on a wide range of materials. Channel waveguide produced by this method on KGd(WO4)2:Yb 3+ [97] and KY(WO4)2:Yb 3+ [97,98] had been reported. A double track writing is required as the process itself induces a reduction of index of refraction on the written track in potassium double tungstates.…”

Section: Waveguides Based On Potassium Double Tungstatesmentioning

confidence: 97%

“…The reported potassium double tungstate waveguide structures which provide two dimensional wave confinement are shown in Figure 2.7. For the ease of discussion they will be referred based on the fabrication method: (a) ultra-fast laser writing [97,98], (b) micro-structured epitaxy layer [99], and (c) epitaxial growth on micro-structured substrate [100].…”

Section: Waveguides Based On Potassium Double Tungstatesmentioning

confidence: 99%

“…A double track writing is required as the process itself induces a reduction of index of refraction on the written track in potassium double tungstates. Figure 2.7(a) shows the cross-sectional view of a waveguide fabricated by ultrafast laser writing [97]. The bright circular beam spot shows a guided beam with reported spot size of 27 µm × 30 µm between two laser written tracks.…”

Section: Waveguides Based On Potassium Double Tungstatesmentioning

confidence: 99%

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Potassium double tungstate waveguides with high ytterbium concentration for optical amplification

Yong

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Cover design: Three dimensional visualization of optical amplification in potassium double tungstate waveguide layer as a signal beam propagates from the top surface to the bottom surface. The model has a radius equivalent to about twenty times the optical beam's radius and only a quarter of the body is shown. The intensity of the signal beam is represented by the color spectrum (red being lowest and blue being highest). The wire frame is generated based on finite element mesh grids.

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Ultrafast laser inscribed Yb:KGd(WO_4)_2 and Yb:KY(WO_4)_2 channel waveguide lasers

Cited by 80 publications

References 23 publications

Raman and fluorescence correlative microscopy in polarized light to probe local femtosecond laser-induced amorphization of the doped monoclinic crystal LYB:Eu

Raman and fluorescence correlative microscopy in polarized light to probe local femtosecond laser-induced amorphization of the doped monoclinic crystal LYB:Eu

Microspectroscopy of ultrafast laser inscribed channel waveguides in Yb:tungstate crystals

Potassium double tungstate waveguides with high ytterbium concentration for optical amplification

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